Try File > Options; on the Advanced pane, there are some Cut, copy, paste settings that might help – or might trip you up later <g>

Alternatively, stop using Ctrl + V for pasting. Press Alt + E; let go, then press S: this brings up the Paste Special dialog where you can select a paste format. Once you feel confident, Alt + E, S, U whizzes you through pasting as unformatted unicode text.